Coating agents based on hydroxyl-containing polycondensation and polyaddition products and their use

ABSTRACT

The present invention relates to coating agents based on hydroxyl-containing binders and isocyanate-containing crosslinking agents, in which coating agents 
     I.) the binder comprises 
     A1) 5 to 80% by weight of at least one polyester or one alkyd resin having an OH number from 0 to 200 mg of KOH/g and an acid number from 0 to 200 mg of KOH/g, 
     A2) 95 to 20% by weight of at least one polyacrylate having an OH number from 30 to 250 mg of KOH/g and an acid number from 0 to 50 mg of KOH/g, 
      the sum of the weight proportions of components (A1) and (A2) being in each case 100% by weight, and 
     II.) the binder is obtainable from 
     1.) at least one polycondensation resin whose acid component comprises 5 to 100 mol % of cycloaliphatic polycarboxylic acids and/or esterifiable derivatives thereof, 
     2.) at least one polyacrylate, at least some of which has been prepared in the presence of the polycondensation resin obtained in the first process step and 
     3.) if desired, at least one further Polyaddition and/or one further Polycondensation resin.

The present invention relates to coating agents based onhydroxyl-containing polycondensation and polyaddition products,comprising

A) a hydroxyl-containing component (A) as binder,

B) at least one polyisocyanate as crosslinking agent,

C) one or more organic solvents,

D) if desired, conventional auxiliaries and additives, in whichcomponents (A) and (B) are present in such amounts that the ratio of thenumber of free OH groups of component (A) to the number of isocyanategroups of component (B) is in the range from 1:3 to 3:1.

The invention furthermore relates to processes for the preparation ofthese coating agents and to the use of the coating agents in automotiverefinishing, in particular as clearcoat.

Coating agents based on a combination of a polycondensation resin and apolyaddition resin are known.

Thus, in German Patent 2,806,497, clearcoats for multilayer coatings aredescribed comprising a mixture of a hydroxyl-containing polyester and ahydroxyl-containing acrylate resin as the binder. The clearcoats containan amino resin as the crosslinking agent. The use of aliphatic and/orcycloaliphatic polycarboxylic acids and aliphatic and/or cycloaliphaticpolyols in the preparation of the polyesters gives clearcoats which,compared with clearcoats based on binders containing aromatic buildingblocks, have improved weathering resistance. However, these clearcoatsdescribed in German Patent 2,806,497 are in need of improvement withrespect to drying capacity and processibility.

Furthermore, many product information sheets from Eastman Kodak oncyclohexanedicarboxylic acid have disclosed that the use ofcyclohexanedicarboxylic acid as the acid component in polyesters whichare used as binders in paints, results in good stability of gloss andcrack resistance of the resulting coatings. However, coating agentsbased on polyesters containing cyclo-hexanedicarboxylic acid have thedisadvantage that while having good drying capacity, they neverthelesshave at the same time only a very limited pot life, i.e. processingtime.

Furthermore, the product information sheet from Bayer AG on Desmophen®A365 has disclosed air-drying automotive repair coatings which contain ahydroxyl-containing binder (Desmophen® A 365) as the binder andpolyisocyanates, such as, for example, Desmodur® N 3390 and Desmodur® N75, as the crosslinking agent. The coatings obtained are distinguishedby a good stability of gloss and by high light stability and chalkingresistance. However, their disadvantage is the extremely short pot lifeof the coating compositions.

Furthermore, German Offenlegungsschrift 3,806,641 has disclosed coatingcompositions which contain a mixture of a carboxyl-containing polyesterand a carboxyl-containing acrylate resin as the binder. Epoxy resins areused in these coating compositions as the crosslinking agent.

Finally, it is known to improve the compatibility of the individualcomponents of binder mixtures by carrying out the synthesis of onecomponent in the presence of the other component.

Accordingly, the present invention is based on the object of providingcoating compositions based on polycondensate resins and polyadditionresins which show rapid drying and simultaneously have a long pot life,i.e. can be processed in the ready-to-use state over a long period oftime. Furthermore, it is desired that the coating compositions are curedat room temperature or slightly elevated temperature, thus enabling themto be used in automotive refinishing. Furthermore, they should at leastfulfil the demands usually made on a clearcoat and possibly haveimproved mechanical properties compared with conventional clearcoats.Thus, the coating compositions should exhibit, for example, goodstability of gloss, crack resistance, filling power and good flowproperties.

Surprisingly, this object is achieved by coating agents based onhydroxyl-containing polycondensation and polyaddition products,comprising

A) a hydroxyl-containing component (A) as binder,

B) at least one polyisocyanate as crosslinking agent,

C) one or more organic solvents,

D) if desired, customary auxiliaries and additives, in which components(A) and (B) are present in such amounts that the ratio of the number offree OH groups of component (A) to the number of isocyanate groups ofcomponent (B) is in the range from 1:3 to 3:1.

In the coating agents,

I.) component (A) comprises

A1) 5 to 80% by weight of at least one polyester and/or one alkyd resin(A1) having an OH number from 0 to 200 mg of KOH/g and an acid numberfrom 0 to 200 mg of KOH/g and

A2) 95 to 20% by weight of at least one polyacrylate (A2) having an OHnumber from 30 to 250 mg of KOH/g and an acid number from 0 to 50 mg ofKOH/g,

the sum of the weight proportions of components (A1) and (A2) being ineach case 100% by weight and

II.) component (A) is obtainable from

1.) at least one polyester and/or one alkyd resin (A1), which isobtainable by reaction of

a) polycarboxylic acids and/or esterifiable derivatives thereof and, ifdesired, monocarboxylic acids, 5 to 100 mol % of this carboxylic acidcomponent being cycloaliphatic polycarboxylic acids and/or esterifiablederivatives thereof,

b) polyols, if desired together with monools,

c) if desired, further modifying components, and

d) if desired, a component capable of reacting with the reaction productfrom a), b) and, if desired, c),

2.) at least one polyacrylate (A2), at least some of which has beenprepared in the presence of the component (A1) obtained in the firstprocess step, and

3.) if desired, at least one further polyaddition and/or one furtherpolycondensation resin.

The invention furthermore relates to processes for the preparation ofthese coating agents and to their use in automotive refinishing, inparticular as clear-coat. In what follows, first the individualcomponents of the coating agents according to the invention are nowillustrated in more detail. The hydroxyl-containing component (A) of thecoating agents according to the invention used as binder comprises

A1) 5 to 80% by weight, preferably 40 to 60% by weight, of at least onepolyester and/or one alky [sic] resin (A1) and

A2) 95 to 20% by weight, preferably 60 to 40% by weight, of at least onepolyacrylate (A2),

the sum of the weight proportions of components (A1) and (A2) being ineach case 100% by weight. The polyesters or alkyd resins used ascomponent (A1) have OH numbers from 0 to 200 mg of KOH/g, preferably 30to 150 mg of KOH/g and acid numbers from 0 to 200 mg of KOH/g,preferably 5 to 50 mg of KOH/g. The number-average molecular weights ofthese polyesters or alkyd resins are usually between 500 and 10,000,preferably between 1000 and 5000, in each case measured by GPC against apolystyrene standard. The polyesters or alkyd resins can, if desired,contain tertiary amino groups.

These polyesters or alkyd resins (A1) are obtainable by reaction of

a) polycarboxylic acids or esterifiable derivatives thereof, if desiredtogether with monocarboxylic acids,

b) polyols, if desired together with monools,

c) if desired, further modifying components and

d) if desired, a component capable of reacting with the reaction productfrom a), b) and, if desired, c).

Carboxylic acid component a) used for preparing the polyesters or alkydresins (A1) comprises 5 to 100 mol %, preferably 30 to 100 mol %, andparticularly preferably 50 to 100 mol %, in each case relative to thetotal amount of component a), of cycloaliphatic polycarboxylic acidsand/or esterifiable derivatives thereof.

Examples of suitable cycloaliphatic polycarboxylic acids aretetrahydrophthalic acid, hexahydrophthalic acid,1,2-cyclohexanedicarboxylic acid, 1,3-cyclohexanedicarboxylic acid,1,4-cyclohexanedicarboxylic acid, 4-methylhexahydrophthalic acid,endomethylenetetrahydrophthalic acid, tricyclodecanedicarboxylic acid,endoethylenehexahydrophthalic acid, camphoric acid,cyclohexanetetracarboxylic acid and cyclobutanetetracarboxylic acid.Preference is given to the use of 1,4-cyclohexanedicarboxylic acid,tetrahydrophthalic acid, hexahydrophthalic acid and alkyl-substitutedderivatives thereof and particular preference to the use of1,4-cyclohexanedicarboxylic acid.

The cycloaliphatic polycarboxylic acids can be used not only in theircis but also in their trans form and as a mixture of both forms.

Examples of suitable polycarboxylic acids, which, if desired, can beused together with the cycloaliphatic polycarboxylic acids, are aromaticand aliphatic polycarboxylic acids, such as, for example, phthalic acid,isophthalic acid, terephthalic acid, halogenophthalic acids, such astetrachloro- or tetrabromophthalic acid, adipic acid, glutaric acid,azelaic acid, sebacic acid, fumaric acid, maleic acid, trimellitic acid,pyromellitic acid, and the like.

Esterifiable derivatives of the abovementioned polycarboxylic acids,such as, for example, mono- or polyesters thereof with aliphaticalcohols having 1 to 4 C atoms or hydroxyalcohols having 1 to 4 C atomsare also suitable. Moreover, the anhydrides of the abovementioned acidscan also be used, if they exist.

If desired, monocarboxylic acids, such as, for example, benzoic acid,tert.-butylbenzoic acid, lauric acid, isononanoic acid and fatty acidsof naturally occurring oils, can also be used together with thepolycarboxylic acids. The preferably used monocarboxylic acid isisononanoic acid.

Suitable alcohol components b) for preparing the polyester or alkydresin (A1) are polyhydric alcohols, such as ethylene glycol,propanediols, butanediols, hexanediols, neopentylglycol, diethyleneglycol, cyclohexanediol, cyclohexanedimethanol, trimethylpentanediol,ethylbutylpropanediol, ditrimethylolpropane, trimethylolethane,trimethylolpropane, glycerol, pentaerythritol, dipentaerythritol,tris(hydroxyethyl) isocyanate, polyethylene glycol, polypropyleneglycol, if desired together with monohydric alcohols, such as, forexample, butanol, octanol, lauryl alcohol, ethoxylated or propoxylatedphenols.

Suitable components c) for preparing the polyesters or alkyd resins (A1)are in particular compounds having a group which is reactive toward thefunctional groups of the polyester, with the exception of the compoundsmentioned as component d). Preferably used modifying components c) arepolyisocyanates and/or diepoxy compounds, if desired alsomonoisocyanates and/or monoepoxy compounds.

Examples of suitable polyisocyanates are toluylene diisocyanates,hexamethylene diisocyanate and isophorone diisocyanate. Diepoxycompounds are understood to mean epoxy resins having on average abouttwo epoxy groups per molecule. Examples of suitable monoepoxy compoundsare olefin oxides, such as octylene oxide, butyl glycidyl ether, allylglycidyl ether, phenyl glycidyl ether, p-butylphenol [sic] glycidylether, cresyl glycidyl ether, styrene oxide, glycidyl methacrylate,cyclohexanevinyl monoxide [sic], dipentene monoxide, α-pinene oxide andglycidyl esters of tertiary carboxylic acids.

Suitable components d) for preparing the polyesters or alkyd resins (A1)are compounds which, apart from a group reactive toward the functionalgroups of polyester (A1), additionally contain a tertiary amino group.

Monoisocyanates having at least one tertiary amino group are preferablyused as components d) reactive with the reaction product from a), b)and, if desired, c). These can be prepared, for example, by reactingsuitable diisocyanates, such as isophorone diisocyanate, with aminoalcohols having a tertiary amino group, such as, for example,hydroxyethylpyridine or dimethylaminoethanol, or with polyamines havingat least one tertiary and at least one secondary or primary amino group.The monoisocyanates are bonded to the binder system by reaction withfree hydroxyl groups of the polycondensation and/or addition productwith the formation of a urethane bond. The components d) used can alsobe polyamines having at least one tertiary and at least one primary orsecondary amino group. An example of these isdimethylaminopropylmethylamine.

If the polyester or alkyd resin (A1) contains ethylenically unsaturateddouble bonds, which are preferably introduced by using ethylenicallyunsaturated components a) and/or b), it is also possible to use mercaptocompounds having at least one tertiary amino group as component d).

In this case, the component a) used is, for example, maleic anhydride orunsaturated fatty acids; an example of an unsaturated alcohol suitableas component b) is 1,4-butenediol. In this case, the mercapto groups ofthe aminothiol having a tertiary amino group undergo an additionreaction with the double bonds introduced into the binder via componenta) and/or b).

Apart from using component d) (polymer-analogous reaction), the tertiaryamino groups can also be introduced into the polyester or the alkydresin (A1) by using amino-containing polyols and/or polycarboxylicacids.

Aminocarboxylic acids having at least one tertiary amino group can beused, for example, together with the cycloaliphatic and, if desired,further polycarboxylic acids, as component a). Examples of these arepyridine-2-carboxylic acid, pyridine-3-carboxylic acid,pyridine-4-carboxylic acid and pyridine-2,6-dicarboxylic acid.Furthermore, the reaction product of an amino alcohol with at least onetertiary amino group and a polycarboxylic anhydride and the reactionproduct of a polyamine having at least one tertiary and at least oneprimary or secondary amino group and a polycarboxylic anhydride can beused.

Amino alcohols having at least one tertiary amino group can be used asalcohol component b). Examples of these are 2-hydroxyethylpyridine,dimethylaminopropanol, methyldiethanolamine, methyldipropanolamine anddihydroxyethylaniline. Reaction products of epoxy resins with carboxylicacids and/or amines can also be used as alcohol component b).

Thus, the reaction product of low-molecular-weight epoxy resins withpolycarboxylic acids and/or polycarboxylic anhydrides andaminocarboxylic acids having at least one tertiary amino group, which isthen, if desired, esterified with the acid and the alcohol componentand, if desired, modified with polyisocyanates, can be used as alcoholcomponent b). Low-molecular-weight epoxy resins are understood to meanepoxy resins having a molecular weight of less than about 2000. Whenepoxy resins are used, types which are low in chlorine should be used,since otherwise strong discoloration of the products can take place.

Polyesters (A1) are prepared by the known methods of esterification (cf.various standard works, such as, for example:

1. Temple C. Patton, Alkyd Resin Technology, Interscience PublishersJohn Wiley & Sons, New York, London 1962;

2. Dr. Johannes Scheiber, Chemie und Technologie der kunstlichen Harze(Chemistry and Technology of Synthetic Resins), WissenschaftlicheVerlagsgesellschaft mbH, Stuttgart, 1943;

3. Hans Wagner+Hans-Friedrich Sarx, Lackkunstharze (Synthetic CoatingResins), 4th edition, Carl Hanser Verlag, Munich, 1959;

4. Ullmanns Encyklopadie der technischen Chemie (Ullmanns Encyclopediaof Industrial Chemistry), volume 14, pages 80 to 106 (1963)).

This reaction is usually carried out at temperatures between 180° and280° C., if desired in the presence of a suitable esterificationcatalyst, such as, for example, lithium octoate, dibutyltin oxide,dibutyltin dilaurate, para-toluenesulfonic acid, and the like.

The preparation of the polyesters or alkyd resins (A1) is usuallycarried out in the presence of small amounts of a suitable solvent asentrainer. Examples of entrainers which are used are aromatichydrocarbons, such as, in particular, xylene and (cyclo)aliphatichydrocarbons, for example cyclohexane.

The polyacrylates used in the coating agents according to the inventionas component (A2) have OH numbers from 30 to 250 mg of KOH/g, preferably50 to 180 mg of KOH/g and acid numbers from 0 to 50 mg of KOH/g,preferably 5 to 20 mg of KOH/g. The number-average molecular weights ofthe polyaddition resins are usually between 1000 and 10,000, preferablybetween 1500 and 6000, measured in each case by GPC against polystyrenestandard. If desired, these polyaddition resins can contain tertiaryamino groups.

It is essential to the invention that at least some of the polyadditionresin (A1) has been prepared in the presence of polycondensation resin(A1). Advantageously, at least 20% by weight and particularlyadvantageously 40 to 80% by weight, of component (A2) are prepared inthe presence of component (A1).

Any residual amount of component (A2) is then added to the bindersolution or the coating agent. This already polymerized resin can havethe same monomer composition as the polyaddition resin synthesized inthe presence of the polycondensation resin. However, it is also possibleto add a hydroxyl-containing polyaddition and/or polycondensation resinhaving a different monomer composition. Furthermore, it is possible toadd a mixture of different polyaddition resins and/or polycondensationresins, one resin of which may have the same monomer composition as thepolyaddition resin synthesized in the presence of the polycondensationresin.

The hydroxyl groups are introduced into the polyaddition resin (A2) byusing hydroxyl-containing monomers. 20 to 60% by weight, preferably 25to 45% by weight, in each case relative to the total weight of themonomers used, of at least one hydroxyl-containing ethylenicallyunsaturated monomer (component p₁) are usually used.

Suitable components p₁) are hydroxyalkyl esters of α,β-unsaturatedcarboxylic acids having primary or secondary hydroxyl groups. If a highreactivity of the acrylate copolymer is desired, it is possible to useexclusively hydroxyalkyl esters having primary hydroxyl groups; if aless reactive polyacrylate is desired, it is possible to use exclusivelyhydroxyalkyl esters having secondary hydroxyl groups. It is of coursealso possible to use mixtures of hydroxyalkyl esters having primaryhxydroxyl groups and hydroxyalkyl esters having secondary hydroxylgroups. Examples of suitable hydroxyalkyl esters of α,β-unsaturatedcarboxylic acids having primary hydroxyl groups are hydroxyethylacrylate, hydroxypropyl acrylate, hydroxybutyl acrylate, hydroxyamylacrylate, hydroxyhexyl acrylate, hydroxyoctyl acrylate and thecorresponding methacrylates. Examples of usable hydroxyalkyl estershaving a secondary hydroxyl group are 2-hydroxypropyl acrylate,2-hydroxybutyl acrylate, 3-hydroxybutyl acrylate and the correspondingmethacrylates. It is of course also possible to use in each case thecorresponding esters of other α,β-unsaturated carboxylic acids, such as,for example, of crotonic acid and isocrotonic acid.

At least some of the component p₁) can advantageously be a reactionproduct of one mol of hydroxyethyl acrylate and/or hydroxyethylmethacrylate with on average two mol of ε-caprolactone. At least some ofthe component P₁) used can also be a reaction product of acrylic acidand/or methacrylic acid with the equivalent amount of a glycidyl esterof a carboxylic acid having a tertiary α-carbon atom. Glycidyl esters ofhighly branched monocarboxylic acids are available under the trade name"Cardura". The reaction of acrylic acid or methacrylic acid with theglycidyl ester of a carboxylic acid having a tertiary α-carbon atom cantake place before, during or after the polymerization reaction. Careshould be taken that the acid number of the finished polyacrylate is inthe range from 5 to 30 mg of KOH/g, preferably 8 to 25 mg of KOH/g.

To prepare the polyaddition resins (A2), in general 0 to 30% by weight,preferably 5 to 20% by weight, in each case relative to the total weightof the monomers used, of at least one vinyl ester of monocarboxylicacids (components p₂) are additionally used. Preferred components p₂)are vinyl esters of monocarboxylic acids branched in the α-position andhaving 5 to 15 C atoms per molecule. The branched monocarboxylic acidscan be obtained by reaction of formic acid or carbon monoxide and waterwith olefins in the presence of a liquid, strongly acidic catalyst; theolefins can be cracking products of paraffinic hydrocarbons, such asmineral oil fractions and can contain both branched and straight-chainacyclic and/or cycloaliphatic olefins. The reaction of olefins of thistype with formic acid or with carbon monoxide and water gives a mixtureof carboxylic acids in which the carboxyl groups are predominantly on aquaternary carbon atom.

Examples of other olefinic starting materials are propylene trimer,propylene tetramer and diisobutylene. The vinyl esters can also beprepared in a manner known per se from the acids, for example byreacting the acids with acetylene.

Because of the ready accessibility, particular preference is given tovinyl esters of saturated aliphatic monocarboxylic acids having 9-11 Catoms which are branched at the α-C atom.

Furthermore, the vinyl ester of p-tertiary-butylbenzoic acid isparticularly preferred. Examples of further suitable vinyl esters arevinyl acetate and vinyl propionate.

To prepare the polyaddition resins (A2), 10 to 80% by weight, preferablyup to 60% by weight, in each case relative to the total weight of themonomers used, of at least one vinylaromatic compound (component p₃) areusually additionally used. Component p₃) preferably contains 8 to 9carbon atoms per molecule. Examples of suitable compounds are styrene,vinyltoluenes, α-methylstyrene, chlorostyrenes, o-, m- orp-methylstyrene, 2,5-dimethylstyrene, p-methoxystyrene,p-tert.-butylstyrene, p-dimethylaminostyrene, p-acetamidostyrene andm-vinylphenol. Preference is given to the use of vinyltoluenes and inparticular styrene.

To synthesize the hydroxyl-containing copolymer (A2), it is furthermorepossible to use 0 to 35% by weight of other, ethylenically unsaturated,copolymerizable monomers (component p₄). The selection of the monomersis not particularly critical. However, care must be taken thatincorporation of these monomers does not lead to undesirable propertiesof the copolymer. Thus, the selection of component p₄) largely dependson the desired properties of the curable composition with respect toelasticity, hardness, compatibility and polarity. Alkyl esters ofolefinically unsaturated carboxylic acids are preferably used ascomponent p₄). Examples of these are methyl (meth)acrylate, ethyl (meth)acrylate, butyl (meth)acrylate, isopropyl (meth)acrylate, isobutyl(meth)acrylate, pentyl ( meth ) acrylate, isoamyl (meth)acrylate, hexyl(meth)acrylate, cyclohexyl (meth)acrylate, 2-ethylhexyl (meth)acrylate,octyl (meth)acrylate, 3,5,5-trimethylhexyl (meth)acrylate, decyl(meth)acrylate, dodecyl (meth)acrylate, hexadecyl (meth)acrylate,octadecyl (meth)acrylate, octadecenyl (meth)acrylate and thecorresponding esters of maleic, crotonic, isocrotonic, vinylacetic anditaconic acid.

Furthermore, other ethylenically unsaturated compounds, such as, forexample, alkoxyethyl acrylates, aryloxyethyl acrylates and thecorresponding methacrylates, such as, for example, butoxyethyl(meth)acrylate and phenoxyethyl (meth)acrylate are suitable as componentp₄). To improve compatibility, it is also possible to incorporate smallamounts of carboxyl-containing monomers by polymerization as componentp₄). Examples of suitable carboxyl-containing monomers are unsaturatedcarboxylic acids, such as, for example, acrylic acid, methacrylic acid,itaconic acid, crotonic acid and monoesters of maleic and fumaric acidand mixtures thereof. By using unsaturated compounds having tertiaryamino groups as component p₄), it is possible to incorporate tertiaryamino groups in copolymer (A2). Examples of suitable monomers areN,N'-diethylaminopropylmethacrylamide [sic], N,N'-diethylaminoethylmethacrylate [sic], 2-vinylpyridine, 4-vinylpyridine, vinylpyrroline,vinylquinoline, vinylisoquinoline, N,N'-dimethylaminoethyl [sic] vinylether and 2-methyl-5-vinylpyridine.

The polymerization of monomer components p₁) to p₄) is preferablycarried out with the exclusion of oxygen, for example by working in anitrogen atmosphere. The reactor is equipped with suitable stirring,heating and cooling devices and with a reflux condenser, in whichvolatile components, such as, for example, stryene, are retained. Thepolymerization reaction is carried out at temperatures from 100° to 180°C., preferably 130°-170° C., with the use of suitable polymerizationinitiators and, if desired, polymerization regulators.

In particular, initiators containing tert.-butyl groups, such as, forexample, di-tert.-butyl peroxide, tert.-butyl hydroperoxide,2,2-di-tert.-butylperoxybutane and1,3-bis(tert.-butylperoxyisopropyl)benzene, and dibenzoyl peroxide aresuitable for preparing the polyaddition resins (A2) in the presence ofpolycondensation resins (A1). These initiators promote a graftingreaction of the acrylate copolymer onto the polyester. Apart from theseabovementioned initiators, the initiators usually used, such as, forexample, dicumyl peroxide, cumyl hydroperoxide, tert.-amyl perbenzoate,tert.-amyl 2-ethylperhexanoate, diacyl peroxides, such as, for example,diacetyl peroxide, peroxyketals, 2,2-di(tert.-amylperoxy)propane, ethyl3,3-di(tert.-amylperoxy)butyrate and thermolabile highly substitutedethane derivatives, for example based on silyl-substituted ethanederivatives and based on benzopinacole, are also [lacuna] for thepreparation of the polyaddition resins (A2) which are not prepared inthe presence of the polycondensation resins (A1). Furthermore, aliphaticazo compounds, such as, for example, azoisovaleronitrile andazobis(cyclohexanenitrile), can also be used.

The amount of initiator is in most cases 0.1 to 8% by weight, relativeto the amount of monomer to be processed, but it can, if desired, alsobe higher. The initiator, which is dissolved in a portion of the solventused for the polymerization is gradually metered in duringpolymerization reaction. Preferably, the initiator feed takes about 0.5to 2 hours longer than the monomer feed, so as to obtain a good effectalso during the afterpolymerization phase. If initiators having only asmall rate of decay are used under the reaction conditions present, itis also possible to initially introduce the initiator.

If desired, the polymerization can be carried out in the presence of aregulator. Suitable regulators are preferably mercapto compounds,mercaptoethanol being used particularly preferably. Examples of otherpossible regulators are alkanethiols, such as, for example,t-dodecanethiol, octanethiol, thiophenol, octadecanethiol, butanethiol,2-ethylhexyl thioglycolate, thiocarboxylic acids, such as, for example,thioacetic acid or thiolactic acid. These regulators are used in anamount of up to 2% by weight, relative to the amount of monomer to beprocessed. Preferably, they are dissolved in one of the monomer feedsand added together with the monomers. The amount of regulator added ispreferably constant with time.

The polymerization is preferably carried out in a high-boiling, organicsolvent which is inert toward the momoners used. Examples of suitablesolvents are higher substituted aromatics, such as, for example, solventnaphtha, heavy benzene, various Solvesso® types, various Shellsol® typesand Deasol® and higher-boiling aliphatic and cycloaliphatichydrocarbons, such as, for example, various white spirits, mineralterpentine oil, tetralin and decalin and various esters, such as, forexample, ethylglycol acetate, butylglycol acetate, ethyldiglycolacetate, and the like. If the monomers used for preparing polyadditionresins (A2) are vinyl esters of monocarboxylic acids (component p₂),copolymerization of components p₁) to p₄) is preferably carried out asfollows, such as also described in EP-A 349,818:

First, at least 60% by weight, preferably 100% by weight, of the totalamount of component p₂) to be used are initially introduced into thereactor together with a portion of the total amount of solvent to beused and heated to the particular reaction temperature. The remainingamount of solvent is, as already described, preferably added graduallytogether with the catalyst. Any residual amount of component p₂) stillpresent and the remaining monomers (components p₁), p₃) and p₄)) aremetered in to the initially introduced component p₂) over a monomeraddition period which is the same for all components (it is in general2-10 h, as is customary for acrylate copolymerizations) in the followingmanner:

i) The amount added per time unit of any component p₂) still present(i.e. the residual amount of component p₂) which was not initiallyintroduced) remains constant or decreases over the monomer additionperiod, the latter process variant being preferred. In the case of aconstant amount being added, component p₂) is preferably metered intogether with components p₁) and p₄).

ii) The amount of components p₁) and p₄) added per time unit remainsconstant within the monomer addition period.

iii) The amount of component p₃) added per time unit is varied withinthe monomer addition period such that the total amount added ofcomponent p₃) within the first third of the monomer addition period is15 to 30% by weight, preferably 18 to 26% by weight, of the total amountof component p₃). Within the second third of the monomer additionperiod, a total of 25 to 40% by weight, preferably 30 to 38% by weight,and within the last third of the monomer addition period 35 to 60% byweight, preferably 40 to 50% by weight, of the total amount of componentp₃) are metered in, the sum of the amounts added in the first, secondand third third being of course 100% by weight.

There are various possibilities of varying the amount of component p₃)added per time unit, the only critical factor being that theabove-mentioned total amounts added in each third are observed. Thus,for example, a stepwise change in the amount of component p₃) added pertime unit is possible. Any desired number of steps in which the amountadded is changed in each case can be selected. Thus, for example, it ispossible to increase the amount added per time unit of component p₃)only at the beginning of the second and/or at the beginning of the thirdthird. Within the third, the amount added per time unit remains then ineach case constant. However, it is also possible to vary the amount ofcomponent added per time unit continuously, in accordance with thelimiting case of an infinite number of steps.

It is assumed that addition of the components in the manner indicatedpromotes copolymerization and reduces homopolymerization of theindividual components.

Preferred coating compositions are obtained if component (A1) and/orcomponent (A2) contain tertiary amino groups. Accordingly, it ispreferred to use polycondensation resins (A1) having an amine numberfrom 5 to 20 mg of KOH/g and/or polyaddition resins (A2) having an aminenumber from 5 to 20 mg of KOH/g. The tertiary amino groups can beintroduced into copolymer (A2) by the additional use of amino-containingmonomers.

However, the hydroxyl-containing polyesters or alkyd resins orcopolymers obtained can also additionally be reacted after thepolymerization in a polymer-analogous reaction with compounds (V),which, apart from a tertiary amino group, additionally contain a groupreactive toward the functional group of the copolymer. Compounds (V)which contain on average 0.8 to 1.5, preferably 1, free isocyanategroups per molecule are preferably used.

The reaction of copolymers (A2) with compounds (V) is carried out in asolvent which is inert to isocyanate, at temperatures from 10° to 100°C., preferably 50° to 80° C., if desired in the presence of organic tincompounds as catalysts, until an NCO value of virtually zero has beenreached. The amount of compound (V) is chosen such that the resultingresin has the above-mentioned amine number.

Compounds (V) which are used for introducing a tertiary amino group intothe binder are prepared by reacting diisocyanates or polyisocyanateswith a less than stoichiometric amount of a tertiary amine. Suitabletertiary amines for this reaction are those of the general formula NR₁R₂ R₃, in which R₁ is preferably an alkanol radical or anotherhydroxyl-containing radical and R₂ or R₃ can be alkyl or cycloalkylradicals. Preference is given to dialkylalkanolamines, such as, forexample, dimethylethanolamine, diethylethanolamine and higher homologsor isomers thereof. Examples of suitable di- or polyisocyanates are:

Aromatic isocyanates, such as, for example, 2,4-, 2,6-toluylenediisocyanate and mixtures thereof, 4,4'-diphenylmethane diisocyanate,m-phenylene diisocyanate, p-phenylene diisocyanate, 4,4-diphenyldiisocyanate, 1,5-naphthalene diisocyanate, 1,4-naphthalenediisocyanate, 4,4-toluidine diisocyanate, xylylene diisocyanate andsubstituted aromatic systems, such as, for example, dianisidinediisocyanates, 4,4-diphenyl ether diisocyanates or chlorodiphenylenediisocyanates and higher functional aromatic isocyanates, such as, forexample, 1,3,5-triisocyanatobenzene,4,4',4"-triisocyanatotriphenylmethane, 2,4,6-triisocyantotoluene and4,4'-diphenyldimethylmethane 2,2', 5,5'-tetraisocyanate; cycloaliphaticisocyanates, such as, for example, 1,3-cylcopentane [sic] diisocyanate,1,4-cyclohexane diisocyanate, 1,2-cyclohexane [lacuna] and isophoronediisocyanate; aliphatic isocyanates, such as, for example, trimethylenediisocyanate, tetramethylene diisocyanate, pentamethylene diisocyanate,hexamethylene diisocyanate, trimethylhexamethylene 1,6-diisocyanate andtris(hexamethylene) triisocyanate.

Diisocyanates having isocyanate groups of different reactivity, such as,for example, isophorone diisocyanate, are preferably used.

Components (A1) and (A2) are preferably used in the coating agents insuch amounts that the binder component (A) has an acid number of at most50 mg of KOH/g, preferably 5 to 20 mg of KOH/g, an OH number from 30 to200 mg of KOH/g, preferably 50 to 150 mg of KOH/g and preferably anamine number from 0 to 20 mg of KOH/g, preferably 5 to 15 mg of KOH/g.

The polyisocyanates used as component (B) for crosslinking thehydroxyl-containing binders are the same polyisocyanates which are alsoused for preparing compound (V). Thus, for suitable examples see thedescription of compound (V). However, the polyisocyanates canfurthermore also be linked to give prepolymers having a higher molecularweight. Of these, adducts of toluylene diisocyanate withtrimethylolpropane, a biuret formed from 3 molecules of hexamethylenediisocyanate and trimers of hexamethylene diisocyanate and3,5,5-trimethyl-1-isocyanato-3-isocyanatomethylcyclohexane may bementioned.

The amount selected of the crosslinking agent used is such that theratio of isocyanate groups of the crosslinking agent to hydroxyl groupsof component (A) is in the range from 1:3 to 3:1.

Combinations with polyisocyanates or resins carrying isocyanate groupsare rapidly crosslinked even at room temperature.

However, it is also possible to use the isocyanates described above,which have been reacted with conventional blocking agents, such as, forexample, phenols, alcohols, acetoacetic esters, ketoxime andε-caprolactam. These combinations are stable at room temperature and arein general only cured at temperatures above 100° C. In special cases,for example if acetoacetic esters are used for blocking, crosslinkingcan also take place even below 100° C.

The coating agents according to the invention contain one or moreorganic solvents as component (C). These solvents are usually used inamounts of 20 to 65% by weight, preferably 30 to 55% by weight, in eachcase relative to the total weight of the coating agent.

Examples of suitable solvents are the abovementioned compounds.

The coating agents according to the invention can furthermore containcustomary auxiliaries and additives in the usual amounts, preferably0.01 to 10% by weight, relative to the total weight of the coating agent(component D). Examples of suitable auxiliaries and additives areflow-improving agents, such as silicone oils, plasticizers, such asphosphoric esters and phthalic esters, viscosity-controlling additives,flatting agents, UV absorbers, light stabilizers and, if desired,fillers.

The coating agents are prepared from components (A) to (D) in a knownmanner by mixing and, if necessary, dispersing the individual components(A) to (D).

These coating agents can be applied to a substrate in the form of a filmby spraying, flooding, dipping, roller application, knife application orbrushing, after which the film is cured to give a firmly adheringcoating.

The curing of these coating agents is usually carried out at roomtemperature or slightly elevated temperature, advantageously attemperatures below 100° C., preferably at temperatures below 80° C.However, the coating agents can also be cured under baking conditions,i.e. at temperatures of at least 100° C.

Suitable substrates are in particular metals and wood, plastic, glass,and the like.

Owing to the short curing times and low curing temperatures, the coatingagents according to the invention are preferably used for automotiverefinishing and the coating of large vehicles and truck superstructures.However, depending on the crosslinking agent used, they can also be usedfor automotive mass-production coating.

Furthermore, they are in particular suitable as clearcoat.

The coating agents according to the invention are distinguished inparticular by a short drying time in combination with longprocessibility (pot life). Furthermore, the resulting coatings, inparticular in the case of clearcoat coatings, have good mechanicalproperties, such as, for example, good stability of gloss, good fillingpower and good flow properties.

Below, the invention is illustrated in more detail by way of exemplaryembodiments. All parts and percentages given are by weight, unlessexpressly stated otherwise.

1. Preparation of Polyesters 1 to 6

The raw materials listed in Table 1 are weighed into a 4 l stainlesssteel boiler equipped with stirrer, steam-heated column and waterseparator. After addition of 4% (relative to the weighed amount ofpolyester raw materials) of xylene as entrainer, the mixture is slowlyheated (over a period of 5-7 hours) to 220° C. The water formed isdistilled off azeotropically. After reaching an acid number of 12-14 mgof KOH/g, the mixture is partly dissolved with Shellsol®A (acommercially available mixture of C3-C4-alkyl-substituted aromatics) toa nonvolatile content of 70%.

                  TABLE 1                                                         ______________________________________                                        Composition of polyesters 1 to 6 in mol                                       Polyester                                                                     resin    1       2       3     4 (C) 5     6 (C)                              ______________________________________                                        PSA      0.77                              1.0                                1,4-CHDA 0.23                        1.0                                      THPSA            1.0                                                          HHPSA                    1.0                                                  IPS                            1.0                                            Trimethylol-                                                                           1.08    1.08    1.08  1.18  1.2   1.07                               propane                                                                       Iosononanoic                                                                           0.62    0.62    0.62  0.70  0.70  0.62                               acid                                                                          Characteristic                                                                values:                                                                       Viscosity                                                                              7.9     3.9     4.55  19    6.6   5.0                                Acid number                                                                            14.7    14.3    13.8  12.3  10.3  12.0                               OH number                                                                              107     107     106   130   140   100                                ______________________________________                                    

(1,4-CHDA=1,4-cyclohexanedicarboxylic acid, HHPSA=hexahydrophthalicanhydride, THPSA=tetrahydrophthalic anhydride, IPS=isophthalic acid,PSA=phthalic anhydride, C=comparison)

OH number and acid number are given in mg of KOH/g; viscosity measuredon a plate/cone viscometer at 23° C., given in dPa·s; amounts given inmol

2. Preparation of Copolymer Solutions 1 to 6

The preparation of the polyester-modified polyaddition resins is carriedout in a 4 l stainless steel boiler equipped with stirrer, refluxcondenser and feed inlets. The initial feeds are in each case thesolutions of the polyester resins and variable amounts of a commerciallyavailable mixture of vinyl esters of saturated aliphatic monocarboxylicacids having predominantly 10 C atoms, which are branched at the α-Catom (commercial product VeoVa® 10 from Shell), and the mixture isheated to 165° C.

Copolymer solution 1

The following are weighed into the boiler and mixed:

998.75 parts of polyester resin 5

118.32 parts of VeoVa® 10

The following are weighed into the monomer feed and mixed:

236.64 parts of methyl methacrylate

236.64 parts of hydroxyethyl methacrylate

591.60 parts of styrene

The following are weighed into the initiator feed and mixed

36.0 parts of di-tert.-butyl peroxide

124.2 parts of Shellsol®A

The monomer mixture is metered in uniformly over a period of four hoursand the initiator mixture over a period of five hours. During thisaddition, the temperature may drop to 160° C. After the initiatoraddition is complete, afterpolymerization of the mixture is allowed tocontinue at 160°-165° C. for another two hours. The copolymer solutionthus obtained has a solids content of 83.6% (15 minutes at 180° C.) anda viscosity, measured as a 55% strength solution in butyl acetate, of3.95 dPa·s. The polymer solution is then partly dissolved with xylene toa solids content of 70% and further dissolved with bytyl [sic] acetateto a solids content of 60%. The viscosity of the 60% strength solutionis 9.1 dPa-s. Acrylate copolymer 1 has an OH number of 86 mg of KOH/g.The mixture has an acid number of 3.6 mg of KOH/g and an OH number of105 mg of KOH/g.

Copolymer Solution 2

The preparation of copolymer solution 2 is carried out similarly to thepreparation of copolymer solution 1. The amounts of polyester precursorand monomer mixture used and the amount of initiator remain the samerelative to one another and are composed as follows:

The following are weighed into the boiler and mixed:

600.00 parts of polyester resin 1

63.00 parts of VeoVa® 10

The following are weighed into the monomer feed and mixed:

126.00 parts of methyl methacrylate

126.00 parts of hydroxyethyl methacrylate

315.00 parts of styrene

The following are weighed into the initiator feed and mixed:

12.6 parts of di-tert.-butyl peroxide

85.60 parts of Shellsol® A

Copolymer solution 2 obtained analogously to the process of copolymersolution 1 has a solids content after polymerization (15 minutes at 180°C.) of 83.4% and a viscosity (measured as a 55% strength solution inbutyl acetate, of 3.2 dPa·s. Analogously to copolymer 1, copolymer 2 isfirst diluted with xylene to a solids content of 70% and then with butylacetate to a solids content of 60%. The original viscosity is 8.8 dPa.s.The acrylate copolymer has an OH number of 86 mg of KOH/g. The mixturehas an acid number of 5.1 mg of KOH/g and an OH number of 95 mg ofKOH/g.

Copolymer Solution 3

The preparation of copolymer solution 3 is carried out similarly to thepreparation of copolymer solution 1. The amounts of polyester precursorand monomer mixture used and the amount of initiator remain the samerelative to one another and have the following composition: Thefollowing are weighed into the boiler and mixed:

600.00 parts of polyester resin 2

63.00 parts of VeoVa® 10

The following are weighed into the monomer feed and mixed:

126.00 parts of methyl methacrylate

126.00 parts of hydroxyethyl methacrylate

315.00 parts of styrene

The following are weighed into the initiator feed and mixed:

12.6 parts of di-tert.-butyl peroxide

85.60 parts of Shellsol®A

Copolymer solution 3 obtained analogously to the process of copolymersolution 1 has a solids content after polymerization (15 minutes at 180°C.) of 82.1% and a viscosity (measured as a 55% strength solution inbutyl acetate, of 5.1 dPa·s. Analogously to copolymer 1, copolymer 3 isfirst diluted with xylene to a solids content of 70% and then with butylacetate to a solids content of 60%. The original viscosity is 18.5dPa·s. The acrylate copolymer 3 has an OH number of 86 mg of KOH/g. Themixture has an acid number of 5.83 mg of KOH/g and an OH number of 95 mgof KOH/g.

Copolymer solution 4

The preparation of copolymer solution 4 is carried out similarly to thepreparation of copolymer solution 1. The amounts of polyester precursorand monomer mixture used and the amount of initiator remain the samerelative to one another and have the following composition:

The following are weighed into the boiler and mixed:

600.00 parts of polyester resin 3

63.00 parts of VeoVa® 10

The following are weighed into the monomer feed and mixed:

126.00 parts of methyl methacrylate

126.00 parts of hydroxyethyl methacrylate

315.00 parts of styrene

The following are weighed into the initiator feed and mixed:

12.6 parts of di-tert.-butyl peroxide

85.60 parts of Shellsol®A

Copolymer solution 4 obtained analogously to the process of copolymersolution 1 has a solids content after polymerization (15 minutes at 180°C.) of 83.5% and a viscosity (measured as a 55% strength solution inbutyl acetate, of 2.3 dPa·s. Analogously to copolymer 1, copolymer 4 isfirst diluted with xylene to a solids content of 70% and then with butylacetate to a solids content of 60%. The original viscosity is 6.05dPa·s. The acrylate copolymer 4 has an OH number of 86 mg of KOH/g. Themixture has an OH number of 95 mg of KOH/g and an acid number of 6.50 mgof KOH/g.

Copolymer Solution 5 (comparison)

The preparation of copolymer solution 5 is carried out similarly to thepreparation of copolymer solution 1. The amounts of polyester precursorand monomer mixture used and the amount of initiator remain the samerelative to one another and have the following composition:

The following are weighed into the boiler and mixed:

600.00 parts of polyester resin 4

63.00 parts of VeoVa® 10

The following are weighed into the monomer feed and mixed:

126.00 parts of methyl methacrylate

126.00 parts of hydroxyethyl methacrylate

315.00 parts of styrene

The following are weighed into the initiator feed and mixed:

12.6 parts of di-tert.-butyl peroxide

85.60 parts of Shellsol®A

Copolymer solution 5 obtained analogously to the process of copolymersolution 1 has a solids content after polymerization (15 minutes at 180°C.) of 81.5% (where the solids content is measured, it is necessary toadd xylene) and a viscosity (measured as a 55% strength solution inbutyl acetate, of 4.6 dPa·s. Analogously to copolymer 1, copolymer 5 isfirst diluted with xylene to a solids content of 70% and then with butylacetate to a solids content of 60%. The original viscosity is 14.0dPa·s. The acrylate copolymer 5 has an OH number of 86 mg of KOH/g. Themixture has an acid number of 5.1 mg of KOH/g and an OH number of 105 mgof KOH/g.

Copolymer solution 6 (Comparison)

The preparation of copolymer solution 6 is carried out similarly to thepreparation of copolymer solution 1. The amounts of polyester precursorand monomer mixture used and the amount of initiator remain the samerelative to one another and have the following composition:

The following are weighed into the boiler and mixed:

600.00 parts of polyester resin 6

63.00 parts of VeoVa® 10

The following are weighed into the monomer feed and mixed:

126.00 parts of methyl methacrylate

126.00 parts of hydroxyethyl methacrylate

315.00 parts of styrene

The following are weighed into the initiator feed and mixed:

12.6 parts of di-tert.-butyl peroxide

85.60 parts of Shellsol® A

Copolymer solution 6 obtained analogously to the process of copolymersolution 1 has a solids content after polymerization (15 minutes at 180°C.) of 81.5% (where the solids content is measured, it is necessary toadd xylene) and a viscosity (measured as a 55% strength solution inbutyl acetate, of 3.5 dPa·s. Analogously to copolymer 1, copolymer 6 isfirst diluted with xylene to a solids content of 70% and then with butylacetate to a solids content of 60%. The original viscosity is 9.0 dPa·s.The acrylate copolymer 6 has an OH number of 86 mg of KOH/g. The mixturehas an acid number of 5.6 mg of KOH/g and an OH number of 92 mg ofKOH/g.

3. Preparation of a Paint Reduction 1

Paint reduction 1 is prepared from the following components:

15 parts of xylene

13 parts of solvent naphtha

10 parts of a commercially available hydrocarbon mixture having aboiling range of 135°-185° C. and an aromatics content of about 16.5%

50 parts of butyl acetate

5 parts of 1-methoxypropyl 2-acetate

3 parts of butylglycol acetate

2 parts of 3-methoxybutyl acetate

2 parts of a commercially available mixture of monocyclic terpeneshaving a boiling range of 162°-182° C.

4. Preparation of a Curing Agent Solution 1

Curing agent solution 1 is prepared from the following components:

50.6 parts of trimerized hexamethylene diisocyanate, 90% strengthsolution in a 1:1 mixture of butyl acetate and solvent naphtha

10.8 parts of solvent naphtha

7.5 parts of xylene

1.5 parts of butyl acetate

14.0 parts of 1-methoxypropyl 2-acetate

11.0 parts of butylglycol acetate

4.0 parts of a 1% strength solution of dibutyltin dilaurate in a 1:1mixture of xylene and butyl acetate

0.6 part of a commercially available silicone oil

Examples 1 to 5 and Comparative Examples 1 to 3

Clearcoat solutions 1 to 8 are prepared from the components listed inTable 2 by mixing.

                                      TABLE 2                                     __________________________________________________________________________    Composition of clearcoats 1 to 8                                                               3    4          7                                            Paint No.  1  2  (Comp.)                                                                            (Comp.)                                                                            5  6  (Comp.)                                                                            8                                       __________________________________________________________________________    Butyl acetate 98/100                                                                     7.2                                                                              7.2                                                                              7.2  7.2  7.2                                                                              7.2                                                                              7.2  7.2                                     Xylene     3.8                                                                              3.8                                                                              3.8  3.8  3.8                                                                              3.8                                                                              3.8  3.8                                     Solvent naphtha                                                                          2.8                                                                              2.8                                                                              2.8  2.8  2.8                                                                              2.8                                                                              2.8  2.8                                     Tinuvin ® 292                                                                        1.2                                                                              1.2                                                                              1.2  1.2  1.2                                                                              1.2                                                                              1.2  1.2                                     Tinuvin ® 1130                                                                       1.0                                                                              1.0                                                                              1.0  1.0  1.0                                                                              1.0                                                                              1.0  1.0                                     Copolymer solution 1                                                                     60.0                                                                             84.0                                                            Copolymer solution 2       84.0                                               Copolymer solution 3          84.0                                            Copolymer solution 4                  84.0                                    Copolymer solution 5             84.0                                         Copolymer solution 6                                                                           84                                                           Copolymer solution 7* 84                                                      Copolymer solution 8*                                                                    24.0                                                               __________________________________________________________________________     *Copolymer solution 7 is Desmophen ° A 365 from Bayer; copolymer       solution 8 is a commercially available Cardura ® E 10 modified OH         acrylate, which is used in automotive repair coatings (commercial product     Macrynal ® SM 513 from Hoechst).                                     

The clearcoat solutions are pre-diluted with paint reduction 1 and thenbrought to a viscosity, measured in the DIN 4 cup at 23° C., of 18seconds with paint reduction 1. The paint solutions are then mixed withcuring agent solution 1 in a mixing ratio of 2:1. In order to determinethe pendulum hardness, coated glass panels are prepared from the paintsby casting, and the films are baked at 60° C. for 30 minutes or left atroom temperature for 24 hours. At a layer thickness of 20 μm (dry), thependulum hardness of the film is then determined. For the other testprocedures, the paint is applied to phospated and coated steel sheets.To this end, the phosphated steel sheets are coated with a commerciallyavailable 2-component polyurethane filler (OHcomponents=polyester-modified hydroxyl-containing acrylate having an OHnumber of 90-110 mg of KOH/g; isocyanate component=hexamethylenediisocyanate trimerized via a biuret structure), dried overnight andthen coated with a commercially available, conventional metallic basecoat (dried by physical means, based on polyester resin, melamine resin,cellulose acetobutyrate, aluminum flakes). After a flash-off time of 30minutes, the clearcoat is applied. The panels are immediately subjectedto the tests described. The results are summarized in Tables 3 and 4.

                                      TABLE 3                                     __________________________________________________________________________    Test results                                                                                        3    4           7                                      Paint No.:    1   2   (Comp.)                                                                            (Comp.)                                                                            5   6  (Comp.)                                                                            8                                 __________________________________________________________________________    Spray viscosity (s)                                                                         18  18  18   18.5 18  18 18   17                                Original viscosity (s)                                                                      36  46  47   90   51  75 60   33                                Additional dilution                                                                         12  11.3                                                                              9.9  26Z  12.1                                                                              18.1                                                                             12.8 8.62                              (parts)                                                                       Viscosity as a function                                                       of time (DIN 4, in seconds)                                                   Initial viscosity                                                                           17  16.5                                                                              16   17   17  16.5                                                                             16.5 16                                after 60 minutes                                                                            19  17.5                                                                              18   18.5 19  18 18   16.5                              after 120 mimutes                                                                           20  19  21   21   20  19 20   18                                after 240 minutes                                                                           23.5                                                                              24  27.5 31   26  22 21.5 21                                after 360 minutes                                                                           33.5                                                                              44  60   --   43  36 95   36                                Pendulum hardness.sup.1)                                                      Room temperature                                                                            65  64  64   59   63  74 78   76                                30', 60° C.                                                                          59  72  72   66   77  81 98   76                                Drying                                                                        Dust-dry.sup.2) after:                                                                      115'                                                                              205'                                                                              170' 170' 115'                                                                              170'                                                                             170' 205'                              Touch-dry.sup.3) after:                                                                     >420'                                                                             >420'                                                                             420' 324' >420'                                                                             325'                                                                             325' >420'                             Drying recorder.sup.4)                                                        1st phase     --  --  --   --   --  -- --   --                                2nd phase      65'                                                                               85'                                                                              145'  50' 130'                                                                               90'                                                                             110' 155'                              3rd phase     205'                                                                              220'                                                                              205' 215' 200'                                                                              205'                                                                             150' 300'                              __________________________________________________________________________

Explanations for Table 3 and Table 4:

1) Pendulum hardness according to Konig in s

2) Dust-dry: about 15 minutes after spraying on the paint, a smallsample of seasand (3-4 g) is spread on a corner of the panel. The panelis then hit from a height of 30 cm with the edge against the ground(free fall). It is dust-dry if no sand adheres. The test is repeatedafter 15 minutes each time, and shortly before it becomes dust-dry therepetition interval is shortened to 5 minutes.

3) Touch-dry:

About 20 minutes after having become dust-dry, the painted panel iscovered with a sheet of paper about 3 cm² in size. A small rigid plasticsheet is placed on this paper, and then a 100 g weight is placed on top.After exactly 1 minute, as in the test for dust dryness, it is testedwhether the paper still adheres. The time interval is as in the test fordust dryness.

Drying recorder:

The test is carried out by the following procedure. It was slightlymodified compared with that of the drying recorder model 504 fromErichsen. Before the steel sheets are coated with the base coat, glassstripes, 25 mm wide and 30 cm long, are glued onto the particular testpanel longitudinally. The test panels along with the glass stripes arethen coated with the base coat and, after a flashoff time of 30 minutes,with the clearcoat. The glass stripes are removed and clamped into aspecial test device (drying recorder). By means of the drying recorder,a needle having a diameter of 1 mm is then moved across the coating fora period of 6 hours. This leads to the formation of three scratchtraces, called phases, caused by the drying of the coating. In the firstphase, the needle penetrates to the glass, and the paint stillcoalesces. In the second phase, a clear scratch trace can be observed,and the paint no longer coalesces. In the third phase, the needlepenetrates into the coating surface only very slightly and only leaves atrace which is barely visible. The middle of transition between twoclearly definable phases is called phase transition.

The tests were carried out in each case at an ambient temperature of26°-28° C.

We claim:
 1. A coating agent based on hydroxyl-containingpolycondensation and polyaddition products, comprisingA) ahydroxyl-containing component (A) as binder, B) at least onepolyisocyanate as crosslinking agent, and C) one or more organicsolvents,in which the components (A) and (B) are present in such amountsthat the ratio of the number of free OH groups of component (A) to thenumber of isocyanate groups of component (B) is in the range from 1:3 to3:1, in which I.) component (A) comprisesA1) 5 to 80% by weight of atleast one polyester and/or one alkyd resin (A1) having an OH number from0 to 200 mg of KOH/g, an acid number from 0 to 200 mg of KOH/g and anumber average molecular weight of between 500 and 10,000 A2) 95 to 20%by weight of at least one polyaddition resin (A2) having an OH numberfrom 30 to 250 mg of KOH/g, an acid number from 0 to 50 mg of KOH/g anda number average molecular weight of between 1,000 and 10,000, the sumof the weight proportions of components (A1) and (A2) being in each case100% by weight and II.) component (A) is obtained from1.) at least onepolyester and/or one alkyd resin (A1), which is obtained by reactionofa) polycarboxylic acids and/or esterifiable derivatives thereof and,optionally, monocarboxylic acids, 5 to 100 mol % of this carboxylic acidcomponent being cycloaliphatic polycarboxylic acids and/or esterifiablederivatives thereof, b) polyols, optionally together with monools, andoptionally, a component capable of reacting with the reaction producefrom a) and b),
 2. 2. ) at least one polyaddition resin (A2), at leastsome of which has been prepared in the presence of component (A1) usingfrom 5 to 30% by weight, based on the total weight of the monomersemployed, of at least one vinyl ester of saturated aliphaticmonocarboxylic acids having 9 to 11 carbon atoms which are branched atthe α carbon atom, and3.) optionally, at least one further polyadditionand/or one further polycondensation resin.
 2. A coating agent as claimedin claim 1, wherein component (A) comprisesA1) 40 to 60% by weight of atleast one polyester and/or one alkyd resin (A1) and A2) 60 to 40% byweight of at least one polyaddition resin (A2).
 3. A coating agent asclaimed in claim 2, wherein 30 to 100 mol % of cycloaliphaticpolycarboxylic acids or esterifiable derivatives thereof have been usedas component a) for preparing the polyester or alkyd resin (A1).
 4. Acoating agent as claimed in claim 1, wherein cyclohexane dicarboxylicacid and/or tetrahydrophthalic acid and/or hexahydrophthalic acid and/oralkyl-substituted derivatives thereof have been used as cycloaliphaticpolycarboxylic acid (component a)) for preparing component (A1).
 5. Acoating agent as claimed in claim 1, whereincyclohexane-1,4-dicarboxylic acid and isononanoic acid have been used ascycloaliphatic polycarboxylic acid (component a)) for preparingcomponent (A1).
 6. A coating agent as claimed in claim 1, whereincomponent (A2) has been prepared using from 5 to 20% by weight, based onthe total weight of the monomers employed, of at least one vinyl esterof saturated aliphatic monocarboxylic acids having 9 to 11 carbon atomswhich are branched at the α carbon atom.
 7. A coating agent as claimedin claim 1, wherein polyesters and/or alkyd resins having an OH numberfrom 30 to 150 mg of KOH/g and an acid number from 5 to 50 mg of KOH/ghave been used as component (A1) and/or polyacrylates having an OHnumber from 50 to 180 mg of KOH/g and an acid number from 5 to 20 mg ofKOH/g have been used as component (A2).
 8. A coating agent as claimed inclaim 7, wherein 40 to 80% by weight of component (A2) have beenprepared in the presence of polyester (A1).
 9. A coating agent asclaimed in claim 1, wherein the polyester and/or alkyd resin (A1) and/orpolyaddition resin (A2) contain tertiary amino groups.
 10. A coatingagent as claimed in claim 1, wherein the polyester and/or alkyd resin(A1) have an amine number from 5 to 20 mg of KOH/g and/or polyacrylate(A2) has an amine number from 5 to 20 mg of KOH/g.
 11. A coating agentas claimed in claim 1, wherein binder (A) has an OH number from 30 to200 mg of KOH/g and an acid number from 5 to 50 mg of KOH/g.
 12. Acoating agent as claimed in claim 1, wherein binder (A) has an OH numberfrom 50 to 150 mg of KOH/g and an acid number from 5 to 20 mg of KOH/g.13. A coating agent as claimed in claim 1, wherein component (A) has anOH number from 80 to 120 mg of KOH/g and an acid number from 5 to 20 mgof KOH/g, component (A1) having an acid number from 0 to 20 mg of KOH/gand component (A2) an acid number from 0 to 20 mg of KOH/g.
 14. Aprocess for the preparation of the coating agent as claimed in claim 1,which comprises mixing and, if necessary, dispersing a mixturecomprisingA) a hydroxyl-containing component (A) as binder, B) at leastone polyisocyanate as crosslinking agent, and C) one or more organicsolvents, D) optionally, conventional auxiliaries and additives,in whichcomponents (A) and (B) are used in such amounts that the ratio of thenumber of free OH groups of component (A) to the number of isocyanategroups of component (B) is in the range from 1:3 to 3:1, in which I.) acomponent (A) is used which comprisesA1) 5 to 80% by weight of at leastone polyester and/or one alkyd resin (A1) having an OH number from 0 to200 mg of KOH/g, an acid number from 0 to 200 mg of KOH/g and a numberaverage molecular weight of between 500 and 10,000, A2) 95 to 20% byweight of at least one polyaddition resin (A2) having an OH number from30 to 250 mg of KOH/g an acid number from 0 to 50 mg of KOH/g and anumber average molecular weight of between 1,000 and 10,000, the sum ofthe weight proportions of components (A1) and (A2) being in each case100% by weight and II.) component (A) is prepared by preparing resin(A1), by1.) reaction ofa) polycarboxylic acids and/or esterifiablederivatives thereof and, optionally, monocarboxylic acids, 5 to 100 mol% of this carboxylic acid component being cycloaliphatic polycarboxylicacids and/or esterifiable derivatives thereof, b) polyols, optionallytogether with monools, and optionally, a component capable of reactingwith the reaction product from a) and b) and,
 2. ) by preparing at leastone polyaddition resin (A2), at least some of which has been prepared inthe presence of component (A1) obtained in the first process step, usingfrom 5 to 30% by weight, based on the total weight of the monomersemployed, of at least one vinyl ester of saturated aliphaticmonocarboxylic acids having 9 to 11 carbon atoms which are branched atthe α carbon atom and3.) by adding any polyacrylate (A2) not prepared inthe presence of polyester (A1) and, optionally at least one furtherpolyaddition and/or polycondensation resin.
 15. Use of the coating agentas claimed in claim 1 for the refinishing of automotive bodies and forthe coating of large vehicles and the coating of truck superstructures.16. Use of the coating agent as claimed in claim 1 as clearcoat.
 17. Thecoating composition of claim 1, wherein the polyester and/or alkyd resin(A1) has a number average molecular weight of between 1,000 and 5,000and the polyaddition resin (A2) has a number average molecular weight ofbetween 1,500 and 6,000.
 18. The process of claim 14, wherein thepolyester and/or alkyd resin (A1) used therein, has a number averagemolecular weight of between 1,000 and 5,000 and the polyaddition resin(A2) used therein, has a number average molecular weight of between1,500 and 6,000.